Image encoding method, image decoding method, image encoding device, image decoding device, and image encoding/decoding device

ABSTRACT

An image encoding method includes: determining whether a current picture is a TSA picture or a trailing picture; and encoding a plurality of pictures according to whether the current picture is the TSA picture or a trailing picture. The determining includes: determining the current picture to be the TSA picture when the current picture does not belong to the highest layer and corresponds to a first field, and determining the current picture to be the trailing picture when the current picture belongs to the highest layer or corresponds to a second field.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of PCT International Application No.PCT/JP2014/003354 filed on Jun. 23, 2014, designating the United Statesof America, which is based on and claims priority of U.S. ProvisionalPatent Application No. 61/843,076 filed on Jul. 5, 2013. The entiredisclosures of the above-identified applications, including thespecifications, drawings and claims are incorporated herein by referencein their entirety.

FIELD

One or more exemplary embodiments disclosed herein relate generally toan image encoding method etc. for encoding a plurality of picturesclassified into a plurality of layers.

BACKGROUND

Non Patent Literature 1 (NPL) discloses a technique relating to an imageencoding method for encoding images (including moving images) or animage decoding method for decoding images.

CITATION LIST Non Patent Literature

Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 andISO/IEC JTC1/SC29/WG11 12th Meeting: Geneva, CH, 14-23 Jan. 2013JCTVC-L1003 v34.doc, High Efficiency Video Coding (HEVC) textspecification draft 10 (for FDIS & Last Call)http://phenix.it-sudparis.eu/jct/doc_end_user/documents/12_Geneva/wg11/JCTVC-L1003-v34.zip

SUMMARY Technical Problem

However, inefficient processes may be performed in the conventionalimage encoding or decoding method.

In view of this, one non-limiting and exemplary embodiment provides animage encoding method for encoding images efficiently or an imagedecoding method for decoding images efficiently.

Solution to Problem

In one general aspect, the techniques disclosed here feature an imageencoding method for encoding, on a per field basis, a plurality ofpictures classified into a plurality of layers for which reference froma picture belonging to a higher layer to a picture belonging to a lowerlayer is prohibited, the plurality of pictures including at least onepicture that is encoded as a temporal sub-layer access (TSA) picture forwhich predetermined reference is prohibited, the image encoding methodincluding: determining whether a current picture included in theplurality of pictures is the TSA picture or a trailing picture for whichthe predetermined reference is permitted; and encoding the plurality ofpictures according to whether the current picture is the TSA picture orthe trailing picture, wherein the determining includes: determining thecurrent picture to be the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is encoded earlier than a second field in a pair offields in a frame; and determining the current picture to be thetrailing picture when the current picture belongs to the highest layeror corresponds to the second field that is encoded later than the firstfield in the pair of fields.

These general and specific aspects may be implemented using a system, adevice, an integrated circuit, a computer program, or a non-transitorycomputer-readable recording medium such as a CD-ROM, or any combinationof systems, devices, integrated circuits, computer programs, orcomputer-readable recording media.

Additional benefits and advantages of the disclosed embodiments will beapparent from the Specification and Drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the Specification and Drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

Advantageous Effects

The image encoding method, the image decoding method, etc. according toone or more exemplary embodiments or features disclosed herein achieveefficient image encoding or decoding.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features will become apparent from thefollowing description thereof taken in conjunction with the accompanyingDrawings, by way of non-limiting examples of embodiments disclosedherein.

FIG. 1 is a diagram illustrating constraint in reference betweenpictures (frames) classified into layers.

FIG. 2 is a diagram illustrating relationships between fields and aframe.

FIG. 3 is a diagram illustrating constraint in reference betweenpictures (fields) classified into layers.

FIG. 4 is a block diagram of an image encoding device according toEmbodiment 1.

FIG. 5 is a flowchart of an image encoding device according toEmbodiment 1.

FIG. 6 is a flowchart of operations performed by a picture typedetermining unit according to Embodiment 1.

FIG. 7 is a diagram illustrating constraint in reference betweenpictures (fields) according to Embodiment 1.

FIG. 8 is a diagram illustrating a modification of constraint inreference between pictures (fields) according to Embodiment 1.

FIG. 9 is a block diagram of an image encoding device according toEmbodiment 2.

FIG. 10 is a flowchart of an image encoding device according toEmbodiment 2.

FIG. 11 is a block diagram of an image decoding device according toEmbodiment 3.

FIG. 12 is a flowchart of an image decoding device according toEmbodiment 3.

FIG. 13 is a flowchart of operations performed by a picture typechecking unit according to Embodiment 3.

FIG. 14 is a flowchart of operations performed by a picture typechecking unit according to Embodiment 3.

FIG. 15 is a block diagram of an image decoding device according toEmbodiment 4.

FIG. 16 is a flowchart of operations performed by an image decodingdevice according to Embodiment 4.

FIG. 17 shows an overall configuration of a content providing system forimplementing content distribution services.

FIG. 18 shows an overall configuration of a digital broadcasting system.

FIG. 19 shows a block diagram illustrating an example of a configurationof a television.

FIG. 20 shows a block diagram illustrating an example of a configurationof an information reproducing/recording unit that reads and writesinformation from and on a recording medium that is an optical disk.

FIG. 21 shows an example of a configuration of a recording medium thatis an optical disk.

FIG. 22A shows an example of a cellular phone.

FIG. 22B is a block diagram showing an example of a configuration of acellular phone.

FIG. 23 illustrates a structure of multiplexed data.

FIG. 24 schematically shows how each stream is multiplexed inmultiplexed data.

FIG. 25 shows how a video stream is stored in a stream of PES packets inmore detail.

FIG. 26 shows a structure of TS packets and source packets in themultiplexed data.

FIG. 27 shows a data structure of a PMT

FIG. 28 shows an internal structure of multiplexed data information.

FIG. 29 shows an internal structure of stream attribute information.

FIG. 30 shows steps for identifying video data.

FIG. 31 shows an example of a configuration of an integrated circuit forimplementing the moving picture coding method according to each ofembodiments.

FIG. 32 shows a configuration for switching between driving frequencies.

FIG. 33 shows steps for identifying video data and switching betweendriving frequencies.

FIG. 34 shows an example of a look-up table in which video datastandards are associated with driving frequencies.

FIG. 35A is a diagram showing an example of a configuration for sharinga module of a signal processing unit.

FIG. 35B is a diagram showing another example of a configuration forsharing a module of the signal processing unit.

DESCRIPTION OF EMBODIMENTS Underlying Knowledge Forming Basis of thePresent Disclosure

The Inventors found the following problems related to the image encodingdevice which encodes images and the image decoding device which decodesimages, described in the “Background” section. These problems aredescribed in detail below.

In recent years, significant technical advancement in digital videodevices have increased cases of compression-coding video signals (of aplurality of pictures arranged in temporal order) input from videocameras or television tuners and recording them onto recording mediasuch as DVDs, hard disks, or the like. There is the H.264/AVC (MPEG-4AVC) as a conventional image coding standard. The high efficiency videocoding (HEVC) standard is currently being considered as thenext-generation standard (Non Patent Literature 1).

According to the current HEVC standard (Non Patent Literature 1), it ispossible to classify pictures as illustrated in FIG. 1 and encode thepictures, with picture reference relationships being restricted. In FIG.1, P_(x) denotes a picture, and _(x) in P_(x) denotes a coding(decoding) order. In FIG. 1, picture layers are illustrated in thevertical direction. TemporalId is an identifier of a layer, and a largernumerical value indicates a deeper layer. The display order of frames isillustrated in the vertical direction (the display order is an inputorder in the image encoding device, and is an output order in the imagedecoding device). In the example of FIG. 1, one frame corresponds to onepicture.

A solid arrow indicates availability (reference permission) of referencefrom a picture indicated by the head (the ending point) of the arrow toa picture indicated by the bottom (the starting point) of the arrow. InFIG. 1, for example, P₁ can refer to P₀. In the example of FIG. 1, P₀can be used to perform inter prediction on P₁ and a prediction image ofP₁ can be generated referring to P₀.

In addition to the reference in the diagram, when a first picture canrefer to a second picture, and the second picture can refer to a thirdpicture, the first picture can refer to the third picture. For example,P₆ can refer to not only P₅ but also P₁ that can be referred to by P₅,and P₀ that can be referred to by P₁.

A broken arrow indicates reference prohibition. In FIG. 1, for example,P₆ cannot refer to P₂. In addition to the reference prohibition in thediagram, when the TemporalId of the second picture is larger than theTemporalId of the first picture, reference from the first picture to thesecond picture is prohibited. For example, P₆ cannot refer to P₄.

Here, reference from a picture belonging to a higher layer (a shallowerlayer) to a picture belonging to a lower layer (a deeper layer) isprohibited. Here, when reference from a picture belonging to a firstlayer to a picture belonging to a second layer is prohibited, the firstlayer is the higher layer (shallower layer) and the second layer is thelower layer (deeper layer).

The purpose of classifying the pictures and encoding the pictures is toprovide a moving image (video) temporal scalability. For example, inFIG. 1, a moving image of 30 fps (frame per second) can be obtained bydecoding only a picture having TemporalId of 0 and a picture havingTemporalId of 1 are decoded from a bitstream of 60 fps corresponding toTemporalId ranging from 0 to 2.

When the TemporalId of a picture PicX is 1 or larger, reference from anyof pictures composed of the picture PicX and the following pictures incoding (decoding) order to an encoded (decoded) picture havingTemporalId larger than or equal to the TemporalId of the picture PicX isprohibited. The picture PicX is included in the pictures composed of thepicture PicX and the following pictures in coding (decoding) order.

For example, in FIG. 1, P₄ having TemporalId of 2 cannot refer to anyencoded (decoded) picture having TemporalId of 2 or larger withreference being prohibited. More specifically, reference from P₄ to P₃is prohibited. Likewise, P₆ having TemporalId of 1 and encoded (decoded)immediately before P₇ cannot refer to any encoded (decoded) picturehaving TemporalId of 1 or larger with reference being prohibited. Morespecifically, reference from P₇ to P₂ is prohibited.

By restricting reference relationships, it is possible to reduce thenumber of reference pictures to be decoded when reproducing a streamstarting at a point other than the starting point in the stream. Forexample, in FIG. 1, when reference relationships are not restricted (inother words, P₇ refers to P₄, and P₄ refers to P₂), pictures are decodedin this order of P₀, P₁, P₂, P₄, P₅, P₆, and P₇ when reproducing P₇.When reference relationships are restricted, pictures are decoded inthis order of P₀, P₁, P₅, P₆, and P₇. In this case, P₂ and P₄ that arereference pictures do not need to be decoded.

Constraint in picture reference relationship is controlled by a flagwhat is called sps_temporal_id_nesting_flag. Whensps_temporal_id_nesting_flag is 1, the picture reference relationship isrestricted as described above. When sps_temporal_id_nesting_flag is 0,no picture reference relationship is restricted, and for example, P₇ mayrefer to P₄ in FIG. 1.

For example, when sps_temporal_id_nesting_flag is 1, a picture havingTemporalId of 1 or larger is encoded (decoded) as a temporal sub-layeraccess (TSA) picture. When a picture PicX is a TSA picture, referencefrom any of pictures composed of the picture PicX and the followingpictures in coding (decoding) order to an encoded (decoded) picturehaving TemporalId larger than or equal to the TemporalId of the picturePicX is prohibited. In this way, reference relationships are restrictedas described above.

However, when reference relationships are restricted as described aboveand the pictures are encoded (decoded) on a per field basis, referencebetween fields having a high correlation may be prohibited. Here, afield structure is a picture structure of a kind for use in encoding(decoding). For example, formats for use in image encoding (decoding)include a frame format and a field format. Stated differently, picturestructures for use in image encoding (decoding) include the framestructure and the field structure.

FIG. 2 is a diagram illustrating relationships between fields and aframe. As illustrated in FIG. 2, the frame includes top fields andbottom fields.

When an image is encoded (decoded) on a per frame basis, the integralframe composed of the top fields and the bottom fields is encoded(decoded). In this case, one frame corresponds to one picture. When animage is encoded (decoded) on a per field basis, the top fields and thebottom fields are separately encoded (decoded). In this case, each field(one field) corresponds to one picture.

FIG. 3 is a diagram illustrating reference constraint in the case wherefields are classified into layers. In FIG. 3, F_(xa) and F_(xb) denotefields, and x denotes a coding (decoding) order. F_(xa) denotes one of atop field and a bottom field, and F_(xb) denotes the other field (thebottom field or the top field).

As illustrated in FIG. 3, in the encoding (decoding) of F_(2b) havingTemporalId of 1 and the following fields, reference to an encoded(decoded) picture having TemporalId of 1 or larger is prohibited withreference being prohibited due to constraint in reference relationship.For this reason, F_(2b) and F_(3a), F_(3a), F_(3b), F_(4a), F_(4b), andF_(2a) cannot be referred to. Likewise, F_(3b) and F_(4b) cannot referto F_(3a) and F_(4a), respectively. One of the fields (the top field orthe bottom field) cannot refer to the other field (the bottom field orthe top field).

Since reference between fields belonging to the same frame and thus aretemporally identical or close to each other is prohibited, which reducesthe accuracy of a prediction image and reduces a compression efficiency.Reference from a picture having TemporalId of 2 to a previously encoded(decoded) field having TemporalId of 1 is prohibited. This referenceconstraint reduces the accuracy of the prediction image and reduces acompression efficiency.

For example, in the case of a still image, F_(2a) and F_(3a) indicatethe same image, and reference from F_(3a) to F_(2a) is prohibited, andthus a prediction image is generated from another image. This reducesthe accuracy of the prediction image and reduces a compressionefficiency.

In one general aspect, the techniques disclosed here feature an imageencoding method for encoding, on a per field basis, a plurality ofpictures classified into a plurality of layers for which reference froma picture belonging to a higher layer to a picture belonging to a lowerlayer is prohibited, the plurality of pictures including at least onepicture that is encoded as a temporal sub-layer access (TSA) picture forwhich predetermined reference is prohibited, the image encoding methodincluding: determining whether a current picture included in theplurality of pictures is the TSA picture or a trailing picture for whichthe predetermined reference is permitted; and encoding the plurality ofpictures according to whether the current picture is the TSA picture orthe trailing picture, wherein the determining includes: determining thecurrent picture to be the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is encoded earlier than a second field in a pair offields in a frame; and determining the current picture to be thetrailing picture when the current picture belongs to the highest layeror corresponds to the second field that is encoded later than the firstfield in the pair of fields.

In this way, the referable picture is appropriately restricted when theplurality of pictures classified into the plurality of layers areencoded on a per field basis. For this reason, it is possible to reducethe amount of processing and a memory capacity, and thus to reducedecrease in prediction accuracy and in compression efficiency.

For example, the encoding may include: encoding an unencoded picturewith the predetermined reference from the unencoded picture to anencoded picture being prohibited, when the current picture is determinedto be the TSA picture, the unencoded picture being the current pictureor a picture following the current picture in coding order in theplurality of pictures, the encoded picture being a picture preceding thecurrent picture in coding order in the plurality of pictures andbelonging to a layer to which the current picture belongs or a layerlower than the layer to which the current picture belongs; and encodingthe unencoded picture with the predetermined reference being permitted,when the current picture is determined to be the trailing picture.

In this way, the reference to the picture encoded before the TSA pictureis restricted. Stated differently, the referable picture isappropriately restricted.

In addition, for example, the determining may include: determining thecurrent picture to be the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field which isa top field; and determining the current picture to be the trailingpicture when the current picture belongs to the highest layer orcorresponds to the second field which is a bottom field.

In this way, in the layers except the highest layer, each of the topfields is determined to be a TSA picture and each of the bottom fieldsis determined to be a trailing picture. Accordingly, the constraint inreference to the top fields is released.

In addition, for example, the determining may include: determining thecurrent picture to be the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field thatimmediately precedes the second field in coding order; and determiningthe current picture to be the trailing picture when the current picturebelongs to the highest layer or corresponds to the second field thatimmediately follows the first field in coding order.

In this way, the constraint in reference to the first field encodedimmediately before the second field is released.

In addition, for example, the image encoding method may further includeencoding a picture type indicating whether the current picture is theTSA picture or the trailing picture.

In this way, for example, it is possible to notify the decoding deviceof the picture type indicating whether the current picture is the TSApicture or the trailing picture.

In one general aspect, the techniques disclosed here feature an imagedecoding method for decoding, on a per field basis, a plurality ofpictures classified into a plurality of layers for which reference froma picture belonging to a higher layer to a picture belonging to a lowerlayer is prohibited, the plurality of pictures including at least onepicture that is decoded as a temporal sub-layer access (TSA) picture forwhich predetermined reference is prohibited, the image decoding methodincluding: identifying whether a current picture included in theplurality of pictures is the TSA picture or a trailing picture for whichthe predetermined reference is permitted; and decoding the plurality ofpictures according to whether the current picture is the TSA picture orthe trailing picture, wherein the identifying includes; identifying thecurrent picture as the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is decoded earlier than a second field in a pair offields in a frame; and identifying the current picture as the trailingpicture when the current picture belongs to the highest layer orcorresponds to the second field that is decoded later than the firstfield in the pair of fields.

In this way, the referable picture is appropriately restricted when theplurality of pictures classified into the plurality of layers aredecoded on a per field basis. For this reason, it is possible to reducethe amount of processing and a memory capacity, and thus to reducedecrease in prediction accuracy and in compression efficiency.

For example, the decoding may include: decoding an undecoded picturewith the predetermined reference from the undecoded picture to a decodedpicture being prohibited, when the current picture is identified as theTSA picture, the undecoded picture being the current picture or apicture following the current picture in decoding order in the pluralityof pictures, the decoded picture being a picture preceding the currentpicture in decoding order in the plurality of pictures and belonging toa layer to which the current picture belongs or a layer lower than thelayer to which the current picture belongs; and decoding the undecodedpicture with the predetermined reference being permitted, when thecurrent picture is identified as the trailing picture.

In this way, the reference to the picture decoded before the TSA pictureis restricted. Stated differently, the referable picture isappropriately restricted.

In addition, for example, the identifying may include: identifying thecurrent picture as the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field which isa top field; and identifying the current picture as the trailing picturewhen the current picture belongs to the highest layer or corresponds tothe second field which is a bottom field.

In this way, in the layers except the highest layer, each of the topfields is identified as a TSA picture and each of the bottom fields isidentified as a trailing picture. Accordingly, the constraint inreference to the top fields is released.

In addition, for example, the identifying may include: identifying thecurrent picture as the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field thatimmediately precedes the second field in decoding order; and identifyingthe current picture as the trailing picture when the current picturebelongs to the highest layer or corresponds to the second field thatimmediately follows the first field in decoding order.

In this way, the constraint in reference to the first field decodedimmediately before the second field is released.

In addition, for example, the image decoding method may further includedecoding a picture type indicating whether the current picture is theTSA picture or the trailing picture, wherein the identifying mayinclude: identifying the current picture as the TSA picture according tothe picture type decoded in the decoding, when the current picture doesnot belong to the highest layer and corresponds to the first field; andidentifying the current picture as the trailing picture according to thepicture type decoded in the decoding, when the current picture belongsto the highest layer or corresponds to the second field.

In this way, for example, it is possible to appropriately identifywhether the current picture is the TSA picture or the trailing pictureaccording to the picture type notified by the encoding device.

In addition, for example, the image decoding method may further includechecking whether the picture type decoded in the decoding is correct,wherein the checking may include: checking that the picture type decodedin the decoding is correct by checking that the picture type indicatesthe current picture as the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field; andchecking that the picture type decoded in the decoding is correct bychecking that the picture type indicates the current picture as thetrailing picture when the current picture belongs to the highest layeror corresponds to the second field.

In this way, the appropriateness of the decoded picture type is checked.Accordingly, decoding operations can be executed according to theappropriate picture type.

In addition, for example, the checking may further include controllingthe decoding of the plurality of pictures so as to prevent decoding ofthe current picture when the picture type decoded in the decoding of thepicture type is incorrect.

In this way, when the decoded picture type is inappropriate, occurrenceof an unexpected trouble is prevented.

These general and specific aspects may be implemented using a system, adevice, an integrated circuit, a computer program, or a non-transitorycomputer-readable recording medium such as a CD-ROM, or any combinationof systems, devices, integrated circuits, computer programs, orcomputer-readable recording media.

Hereinafter, certain embodiments are described in detail with referenceto the Drawings. Each of the embodiments described below illustrates ageneral or specific example. The numerical values, shapes, materials,constituent elements, the arrangement and connection of the constituentelements, steps, the processing order of the steps etc. shown in thefollowing embodiments are mere examples, and therefore do not limit thescope of the claims. In addition, among the constituent elements in thefollowing exemplary embodiments, constituent elements not recited in anyone of the independent claims which define the most generic concept aredescribed as arbitrary constituent elements.

Hereinafter, coding may be used to mean encoding.

Embodiment 1 Overall Configuration

FIG. 4 illustrates a configuration of an image encoding device accordingto this embodiment. The image encoding device 100 includes: a picturetype determining unit 101; a dividing unit 102; a subtractor 103; atransform and quantization unit 104; an encoding unit 105; an inversetransform and quantization unit 106; an adder 107; a frame memory 108;an intra prediction unit 109; and an inter prediction unit 110. Forexample, these constituent elements are exclusive or general-purposecircuitry.

<Operations (Overall)>

Next, an overall encoding flow is described with reference to FIG. 5.

First, the picture type determining unit 101 determines a picture typeof a current picture to be encoded (S101). This is described in detaillater. It is to be noted that a picture type indicates whether a pictureis a temporal sub-layer access (TSA) picture or a trailing picture.

Stated differently, the picture type corresponds to either the TSApicture or the trailing picture. The picture type may correspond toanother picture. The other picture is, for example, what is called aleading picture. The picture type may correspond either an I-picture, aP-picture, or a B-picture. The picture type may also correspond to acombination of a plurality of picture types.

Next, the encoding unit 105 encodes picture information including areference constraint flag, a picture structure, a field number,TemporalId, a field classification, a picture type, etc. (S102).

Here, the reference constraint flag is a flag indicating whether or nota reference relationship between pictures is restricted. The picturestructure is either a frame structure or a field structure, andindicates whether an input image has a frame structure or a fieldstructure. It is to be noted that information indicating a picturestructure may be simply represented as a picture structure. The fieldnumber is a number corresponding to a display order of a field. Thefield number may be a picture number that is the number corresponding tothe display order of a picture. TemporalId is an identifier indicating alayer to which a current picture to be encoded belongs.

The field classification is a classification (identifier) indicatingwhether a current field to be encoded is a first field or a secondfield. The first field is a field that is encoded earlier than a secondfield in a pair of fields in a frame, and the second field is a fieldthat is encoded later than the second field in the pair of fields in theframe. In FIG. 3, F_(xa) is a first field, and F_(xb) is a second field.

Next, the dividing unit 102 divides an input image into a plurality ofblocks (S103). For example, each of the blocks is also referred to as acoding unit in a coding standard.

Next, the intra prediction unit 109 and the inter prediction unit 110each derives prediction information including a prediction block, acost, a prediction mode, etc. in a corresponding one of intra predictionand inter prediction (S104, S105). The intra prediction unit 109 and theinter prediction unit 110 determine the prediction mode and theprediction block based on the derived prediction information (S106).

Next, the subtractor 103 obtains a difference between the predictionblock and the original block to generate a residual block (S107). Thetransform and quantization unit 104 performs frequency transform andquantization on the residual block (S108). Next, the inversequantization unit 106 performs inverse quantization and inversetransform to reconstruct the residual block (S109). Next, the adder 107adds (sums) the residual block and the prediction block to generate adecoded block (decoded image) (S110).

Next, the encoding unit 105 encodes the prediction information (S111).In addition, the encoding unit 105 encodes transform coefficientsgenerated through the frequency transform and quantization (S112).

Next, when processing on all of the blocks has not yet been completed(No in S113), the image encoding device 100 selects a next block (S114).The image encoding device 100 repeats the above described processes(S104 to S112) until processing on all of the blocks in the picture hasbeen completed. In addition, when processing on all of the pictures hasnot yet been completed (No in S115), the image encoding device 100selects a next picture (S116). Next, the image encoding device 100repeats the above described processes (S101 to S114) until processing onall of the pictures has been completed.

Hereinafter, the picture type determining unit 101 is mainly describedin detail.

<Operations (Determination of Picture Types)>

Next, a picture type determination flow is described with reference toFIG. 6. Here, a picture type is determined for each picture.Specifically, the picture type is determined for each of access unitswhich corresponds to the picture. A picture encoded on a per field basiscorresponds to fields. On the other hand, a picture encoded in framestructure corresponds to a frame.

First, when TemporalId is 0 (No in S201), or when a reference constraintflag is 0 (No in S202), the picture type determining unit 101 determinesthe picture type of a current picture to be encoded is a trailingpicture (S208). In other words, in each of these cases, the picture typedetermining unit 101 determines that the current picture to be encodedis a trailing picture. Here, the case in which the reference constraintflag is 0 means that no reference is restricted.

Next, when the picture structure is the frame structure (No in S203),the picture type determining unit 101 determines that the picture typeof the current picture to be encoded is a TSA picture (S207). In otherwords, in each of these cases, the picture type determining unit 101determines that the current picture to be encoded is a TSA picture.

Next, when the field classification indicates a first field (No inS204), the picture type determining unit 101 determines that the currentpicture to be encoded is a TSA picture (S207).

Next, when the field that precedes by one the current field to beencoded in coding order is a first field in a frame (Yes in S205), thepicture type determining unit 101 determines that the current picture tobe encoded is a trailing picture (S206). Otherwise (No in S205), thepicture type determining unit 101 determines that the current picture tobe encoded is a TSA picture (S207). Whether or not the field thatprecedes by one the current picture to be encoded in coding order is afirst field is determined based on a field number indicating the numbercorresponding to the display order of the preceding field.

As described above, the TSA picture is a picture with reference beingprohibited from any of pictures composed of the TSA picture and thefollowing pictures in coding (decoding) order to an encoded (decoded)picture having TemporalId larger than or equal to the TemporalId of theTSA picture. The trailing picture is a picture with reference permittedfrom any of pictures composed of the trailing picture and the followingpictures in coding (decoding) order to an encoded (decoded) picturehaving TemporalId larger than or equal to the TemporalId of the trailingpicture.

<Effects>

Hereinafter, in this embodiment, when reference is restricted, referencecan be made from one of the fields (either the top field or the bottomfield) to the other field (the bottom field or the top field). Thisincreases a prediction accuracy. In other words, the image encodingdevice 100 according to this embodiment is capable of achieving bothconstraint of reference relationship and reduction in decrease incompression efficiency.

More specifically, in this embodiment, reference relationships in FIG. 3are modified to reference relationships in FIG. 7. In FIG. 7, a secondfield is not a TSA picture but a trailing picture (TP). Accordingly,reference can be made to a field temporally identical or close theretoin the same frame. For example, reference from F_(2b) to F_(2a) can bemade. This increases a prediction accuracy.

In addition, reference to a first field belonging to another layer canbe made. For example, reference from F_(3a) to F_(2a) can be made. Thisincreases a prediction accuracy. In addition, both increase inprediction accuracy and constraint in reference relationship areachieved.

Examples of prohibited reference include reference from any of fieldscomposed of a field F_(2a) having TemporalId of 1 and the followingfields to be encoded (decoded) after F_(2a) to a field encoded (decoded)prior to F_(2a) and having TemporalId of 1 or larger. Accordingly, inreproduction starting with a field other than the starting field in apicture, it is possible to reduce the number of reference pictures to bedecoded.

By means of the image encoding device 100 encoding the referenceconstraint flag, the image decoding device can find the referenceconstraint before decoding of the field is started. For this reason, theimage decoding device can skip a process of decoding a field that is notreferred to by any field. Accordingly, the image decoding device canreduce the amount of processing.

When reference is restricted, time until a processed field is notreferred to any longer by another field is shorter than the case whereno reference is restricted. For this reason, it is possible to discardthe processed field from the frame memory 108 at an earlier time.Accordingly, it is possible to reduce the size of the frame memory 108.The image decoding device can find the frame memory size that should besecured according to the reference constraint flag at the earlier time.Accordingly, the image decoding device can secure the system resource atthe earlier time.

The hierarchical structure illustrated in FIG. 7 is an example, and thushierarchical structures are not limited to the example in FIG. 7. Forexample, a two-layer hierarchical structure as in FIG. 8 is alsopossible. Such a modification is possible using TemporalId that is inputfrom outside.

In this embodiment, the reference constraint flag is input from outside.However, the reference constraint flag may not input from outside. Forexample, reference may be always restricted, reference may be restrictedwhen an image is encoded on a per field basis, or the value of areference constraint flag may be determined according to a codingcondition. Alternatively, any reference constraint flag may not beencoded.

For example, reference constant in encoding and decoding may be alwaysdetermined in advance. The image decoding device may derive a picturetype from a field number, a field classification, a picture structure,or TemporalId.

Furthermore, the image encoding device 100 may usesps_temporal_id_nesting_flag conforming to the current HEVC standard(Non Patent Literature 1). As in this embodiment, when reference isrestricted, the image encoding device 100 may setsps_temporal_id_nesting_flag to 1, and may encode thesps_temporal_id_nesting_flag.

In this embodiment, TemporalId is input from outside. However,TemporalId may not be input from outside. For example, the imageencoding device 100 may include a TemporalId setting unit. TheTemporalId setting unit may set TemporalId for each of input picturesaccording to a predetermined method. The predetermined method may be,for example, a method for incrementing TemporalId by 1 for each picture,and returning the incremented TemporalId to 0 at three-pictureintervals.

In addition, any picture structure, field number, and fieldclassification may not be input from outside. They may be fixed values,or be determined according to a predetermined method.

In this embodiment, each picture type is determined by deciding whetherthe field that immediately precedes the current field in coding order isone of the first fields in the same frame, based on the field number ofthe preceding field. Picture type determination methods are not limitedto the method.

For example, when a current field is a second field, the field thatimmediately precedes the current field in coding order may be alwaysdetermined to be one of the first fields in the same frame in advance.The second field may be determined to be a trailing picture irrespectiveof the immediately previous field. In this case, the field number maynot be input to the picture type determining unit 101 as a matter ofcourse.

A top field is set as a first field, and a bottom field is set as asecond field. Inversely, a bottom field is set as a first field, and atop field is set as a second field. Furthermore, these settings may beswitched in a point other than the starting point in a process.

The whole or part of picture information including a referenceconstraint flag, a picture structure, a field number, TemporalId, afield classification, etc. may be encoded at the beginning of a sequenceincluding a plurality of pictures, at the beginning of a picture or afield, or at the beginning of a slice. The whole or part of the pictureinformation may be encoded as a part of supplemental enhancementinformation (SEI) according to the current HEVC standard (Non PatentLiterature 1).

When a premise that reference is restricted is predetermined, adetermination (S202 in FIG. 6) based on a reference constraint flag maynot be made. When a premise that a picture structure is a fieldstructure is predetermined, a determination based on the picturestructure may not be made (S203 in FIG. 6). When a premise that a secondfield in the same frame including a first field is encoded immediatelyafter the first field, a determination (S205 in FIG. 6) based on theimmediately previous current field to be encoded may not be made.

Furthermore, a process in this embodiment may be executed usingsoftware. The software may be distributed by download etc. The softwaremay be recorded on a recording medium such as a CD-ROM, and bedistributed. This applies to the other embodiments in the presentDescription as a matter of course.

Embodiment 2

In this embodiment, main characteristics of the image encoding devicedescribed in Embodiment 1 are indicated.

FIG. 9 is a block diagram of an image encoding device according to thisembodiment. An image encoding device 300 illustrated in FIG. 9 includesa determining unit 301 and an encoding unit 302. The determining unit301 corresponds to the picture type determining unit 101 in FIG. 4. Theencoding unit 302 corresponds to the dividing unit 102, the subtractor103, the transform and quantization unit 104, the encoding unit 105, theinverse quantization unit 106, the adder 107, the frame memory 108, theintra prediction unit 109, and the inter prediction unit 110 in FIG. 4.

FIG. 10 is a flowchart of operations performed by the image encodingdevice 300 illustrated in FIG. 9. It is to be noted as a premise thatthe image encoding device 300 encodes, on a per field basis, a pluralityof pictures classified into a plurality of layers for which referencefrom a picture belonging to a higher layer to a picture belonging to alower layer is prohibited. The image encoding device 300 restrictsreference as a premise. More specifically, the image encoding device 300encodes at least one of the plurality of pictures as a TSA picture forwhich predetermined reference is prohibited.

First, the determining unit 301 determines whether a current pictureincluded in the plurality of pictures is a TSA picture or a trailingpicture for which the predetermined reference is permitted. Stateddifferently, the determining unit 301 determines the picture type of thecurrent picture (S301).

When the current picture here does not belong to the highest layer andcorresponds to a first field, the determining unit 301 determines thatthe current picture is a TSA picture. When the current picture belongsto the highest layer, or corresponds to a second field, the determiningunit 301 determines that the current picture is a trailing picture.

Here, the first field is a field that is encoded earlier than a secondfield in a pair of fields in a frame. The second field is a field thatis encoded later than the first field in the pair of fields in theframe.

Next, the encoding unit 302 encodes the plurality of pictures accordingto whether the current picture is the TSA picture or the trailingpicture (S302).

For example, when the current picture is determined to be the TSApicture, the encoding unit 302 encodes an unencoded picture withpredetermined reference being prohibited. When the current picture isdetermined to be the trailing picture, the encoding unit 302 encodes anunencoded picture with the predetermined reference being permitted.

Here, the unencoded picture is any of pictures composed of the currentpicture and the following pictures in coding order among the pluralityof pictures. The predetermined reference is reference from the unencodedpicture to an encoded picture that is the picture preceding the currentpicture in coding order among the plurality of pictures and belonging toa layer to which the current picture belongs or a layer below the layerto which the current picture belongs.

The first field may be a top field, and the second field may be a bottomfield. Accordingly, settings that a first field is a top field and asecond field is a bottom field may be determined in advance. Asillustrated in FIG. 2, the top field is a field spatially located abovea bottom field, and the bottom field is a field spatially located belowthe top field.

When the current picture belongs to the highest layer or corresponds tothe second field, and when the picture immediately preceding the currentpicture in decoding order corresponds to the first field in a frameincluding the current picture, the determining unit 301 may determinethe current picture to be a trailing picture. The determining unit 301may determine the current picture to be a TSA picture in the othercases.

In short, the second field may be the field immediately following thefirst field in coding order. The first field may be the fieldimmediately preceding the second field in coding order. In addition, apair of fields in a frame may be predetermined to be encodedsequentially.

The encoding unit 302 may encode a picture type indicating whether acurrent picture is a TSA picture or a trailing picture.

Embodiment 3 Overall Configuration>

FIG. 11 illustrates a configuration of an image decoding deviceaccording to this embodiment. The image decoding device 400 illustratedin FIG. 11 includes: a picture type checking unit 412; a decoding unit411; an inverse transform and quantization unit 406; an adder 407; aframe memory 408; an intra prediction unit 409; and an inter predictionunit 410. For example, these constituent elements are exclusive orgeneral-purpose circuitry.

<Operations (Whole)>

Next, an overall decoding flow is described with reference to FIG. 12.

First, the decoding unit 411 decodes picture information included in abitstream (S401). More specifically, the decoding unit 411 decodes areference constraint flag, a picture type, TemporalId, a field number, afield classification, and a picture structure.

Next, the picture type checking unit 412 checks the picture type of acurrent picture (S402). Stated differently, the picture type checkingunit 412 determines whether or not the decoded picture type is correct.This is described in detail later.

When the picture type is incorrect, stated differently, when the picturetype is erroneous (Yes in S403), the picture type checking unit 412outputs information indicating that the picture type is erroneous(S412). For example, in this case, the image decoding device 400displays indication of the error for the display device and ends thedecoding process of the current picture.

Next, the decoding unit 411 decodes prediction information (S404). Whena prediction mode included in the prediction information is intraprediction (Yes in S405), the intra prediction unit 409 generates aprediction block based on intra prediction (S406). When a predictionmode is inter prediction (No in S405), the inter prediction unit 410generates a prediction block based on inter prediction (S407).

Next, the decoding unit 411 decodes transform coefficients (S408) Next,the inverse transform and quantization unit 406 performs inversequantization and inverse transform on the decoded transform coefficientsto reconstruct the residual block (S409). Next, the adder 407 adds(sums) the residual block and the prediction block to generate a decodedblock (decoded image) (S410).

Next, when processing on all of the blocks has not yet been completed(No in S411), the image decoding device 400 selects a next block (S412).The image encoding device 400 repeats the above described processes(S404 to S410) until processing on all of the blocks in a picture hasbeen completed. In addition, when processing on all of the pictures hasnot yet been completed (No in S414), the image decoding device 400selects a next picture (S415). Next, the image decoding device 400repeats the above described processes (S401 to S413) until processing onall of the pictures has been completed.

The image decoding device 400 may discard, from the frame memory 408, apicture that is not referred to any longer from another picture becauseof reference constraint based on a reference constraint flag, appearanceof a TSA picture, etc. The image decoding device 400 does not need todecode the picture that is not referred to by any picture when decodinga stream starting from a point other than the starting point in astream.

<Operations (Picture Type Check)>

Next, a picture type check flow is described with reference to FIGS. 13and 14.

First, when the TemporalId is 0 (No in S501) or the reference constraintflag is 0 (No in S502), the picture type checking unit 412 sets acorrect picture type to a trailing picture (S508).

Next, when the picture structure is a frame structure (No in S503), thepicture type checking unit 412 sets a correct picture type to a TSApicture (S507).

Next, when the field classification indicates a first field (No inS504), the picture type checking unit 412 sets a correct picture type toa TSA picture (S507).

Next, when the immediately previous field in decoding order is a firstfield in the same frame (Yes in S505), the picture type checking unit412 sets a correct picture type to a trailing picture (S506). Otherwise,the picture type checking unit 412 sets a correct picture type to a TSApicture (S507). Whether or not the immediately previous field indecoding order is the first field is determined based on a field numberindicating the display order of the field.

Next, the picture type checking unit 412 checks whether or not thepicture type decoded by the decoding unit 411 is identical to thecorrect picture type (S509). When the picture type decoded by thedecoding unit 411 is different from the correct picture type (No inS509), the picture type checking unit 412 determines that the picturetype is erroneous (S510).

<Effects>

As described above, the image decoding device 400 in this embodiment candecode a bitstream encoded by the image encoding device 100 inEmbodiment 1. The image decoding device 400 in this embodiment usespicture types as in Embodiment 1, and thus can obtain effects similar tothose obtained in Embodiment 1.

The image decoding device 400 can determine whether or not a picturetype in a bitstream is correct by checking the picture type.Accordingly, the image decoding device 400 can detect a corruptbitstream. The image decoding device 400 can prevent occurrence of astate in which: a decoding process on a corrupt bitstream fails, andthus can prevent a state in which the decoding process cannot be endedcorrectly.

The image decoding device 400 can find that reference is restrictedaccording to the reference constraint flag prior to decoding. For thisreason, the image decoding device 400 can skip a process of decoding afield that is not referred to by any field. Accordingly, the imagedecoding device 400 can reduce the amount of processing.

When reference is restricted, time until a processed field is notreferred to any longer by another field is shorter than the case whereno reference is restricted. For this reason, the image decoding device400 can discard a processed field from the frame memory 408 at anearlier time, and thus can decode an image using the frame memory 408having a small size.

The image decoding device 400 can find the frame memory size that shouldbe secured according to the reference constraint flag at the earliertime. Accordingly, the image decoding device 400 can secure the systemresource at the earlier time.

In this embodiment, the reference constraint flag is included in abitstream. However, the reference constraint flag may not be included ina bitstream. For example, reference may be always restricted, referencemay be restricted when an image is decoded on a per field basis, or thevalue of a reference constraint flag may be determined according to adecoding condition.

In addition, sps_temporal_id_nesting_flag according to the current HEVCstandard (Non Patent Literature 1) may be used as a reference constraintflag. For example, a determination that reference is restricted may bemade when sps_temporal_id_nesting_flag is 1.

The whole or part of picture information including a referenceconstraint flag, a picture structure, a field number, TemporalId, afield classification, etc. may be decoded at the beginning of a sequenceincluding a plurality of pictures, at the beginning of a picture or afield, or at the beginning of a slice. The whole or part of the pictureinformation may be decoded as a part of supplemental enhancementinformation (SEI) according to the current HEVC standard (Non PatentLiterature 1).

When decoding picture information at the beginning of a sequence, theimage decoding device 400 may decode all of the plurality of picturesafter checking that all of the picture types of the plurality ofpictures are correct. When the picture types of the plurality ofpictures are partly incorrect, the image decoding device 400 may skipdecoding of a picture having an incorrect picture type, or may stop thewhole decoding of the plurality of pictures.

Embodiment 4

In this embodiment, main characteristics of the image decoding devicedescribed in Embodiment 3 are indicated.

FIG. 15 is a block diagram of an image decoding device according to thisembodiment. The image decoding device 600 illustrated in FIG. 15includes an identifying unit 601 and a decoding unit 603. Theidentifying unit 601 corresponds to part of the decoding unit 411 inFIG. 11. The decoding unit 603 includes constituent elements in FIG. 11that are: the other part of the decoding unit 411; the inverse transformand quantization unit 406; the adder 407; the frame memory 408; theintra prediction unit 409; and the inter prediction unit 410.

The image decoding device 600 may include a checking unit 602, or maynot include the checking unit 602. The checking unit 602 corresponds tothe picture type checking unit 412 in FIG. 11.

FIG. 16 is a flowchart of operations performed by the image decodingdevice 600 illustrated in FIG. 15. It is to be noted as a premise thatthe image decoding device 600 decodes, on a per field basis, a pluralityof pictures classified into a plurality of layers for which referencefrom a picture belonging to a higher layer to a picture belonging to alower layer is prohibited. The image encoding device 600 restrictsreference as a premise. More specifically, the image decoding device 600decodes at least one of the plurality of pictures as a TSA picture forwhich predetermined reference is prohibited.

First, the identifying (determining) unit 601 identifies (determines)whether a current picture included in the plurality of pictures is a TSApicture or a trailing picture for which the predetermined reference ispermitted. Stated differently, the identifying unit 601 determines apicture type of the current picture (S601).

When the current picture here does not belong to the highest layer andcorresponds to a first field, the identifying unit 601 identifies thatthe current picture as a TSA picture. When the current picture belongsto the highest layer, or corresponds to a second field, the identifyingunit 601 identifies the current picture as a trailing picture.

Here, the first field is a field that is decoded earlier than a secondfield in a pair of fields in a frame. Here, the second field is a fieldthat is decoded later than the first field in the pair of fields in theframe.

Next, the decoding unit 603 decodes a plurality of pictures according towhether a current picture is a TSA picture or a trailing picture (S603).

For example, when the current picture is identified as a TSA picture,the decoding unit 603 decodes an undecoded picture with predeterminedreference being prohibited. When the current picture is identified as atrailing picture, the decoding unit 603 decodes an undecoded picturewith predetermined reference being permitted.

Here, the undecoded picture is any of pictures composed of the currentpicture or the following pictures in decoding order among the pluralityof pictures. The predetermined reference is reference from the undecodedpicture to a decoded picture that is the picture preceding the currentpicture in decoding order among the plurality of pictures and belongingto a layer to which the current picture belongs or a layer below thelayer to which the current picture belongs.

The first field may be a top field. The second field may be a bottomfield. Accordingly, settings that a first field is a top field and asecond field is a bottom field may be determined in advance. Asillustrated in FIG. 2, the top field is a field spatially located abovea bottom field, and the bottom field is a field spatially located belowthe top field.

When the current picture belongs to the highest layer or corresponds toa second field, and when the picture immediately preceding the currentpicture in decoding order corresponds to a first field in a frameincluding the current picture, the identifying unit 601 may identify thecurrent picture as a trailing picture. The identifying unit 601 mayidentify the current picture as a TSA picture in the other cases.

In short, the second field may be the field immediately following thefirst field in decoding order. The first field may be the fieldimmediately preceding the second field in decoding order. In addition, apair of fields in a frame may be predetermined to be decodedsequentially.

The decoding unit 603 may decode a picture type indicating whether acurrent picture is a TSA picture or a trailing picture.

For example, when the current picture here does not belong to thehighest layer and corresponds to a first field, the identifying unit 601identifies that the current picture as a TSA picture according to thepicture type decoded by the decoding unit 603. For example, when thecurrent picture belongs to the highest layer or corresponds to a secondfield, the identifying unit 601 identifies the current picture as atrailing picture according to the picture type decoded by the decodingunit 603.

As described above, the image decoding device 600 may include thechecking unit 602 which checks that the picture type decoded by thedecoding unit 603 is correct. The checking unit 602 checks that thedecoded picture type of the current picture is correct prior to decodingthe current picture (S602).

For example when the current picture does not belong to the highestlayer and corresponds to the first field, the checking unit 602 checksthat the picture type decoded by the decoding unit 603 indicates thatthe current picture is the TSA picture. For example, when the currentpicture belongs to the highest layer and corresponds to the secondfield, the checking unit 602 checks that the picture type decoded by thedecoding unit 603 indicates that the current picture is the trailingpicture.

In this way, the checking unit 602 checks that the picture type decodedby the decoding unit 603 is correct. When the picture type decoded bythe decoding unit 603 is incorrect, the checking unit 602 may controldecoding of the plurality of pictures so that the current picture is notdecoded. For example, the checking unit 602 may allow the decoding unit603 to skip decoding of a current picture by notifying the decoding unit603 of the fact that the picture type decoded by the decoding unit 603is incorrect.

In each of the above embodiments, each of the constituent elements isimplemented by circuitry including, for example, an MPU, memory, etc.The processes executed by the respective constituent elements may beexecuted by software (a program). The software is, for example, recordedon a recording media such as a ROM. The software may be distributed bydownloading or the like, or may be recorded on recording media such asCD-ROMs and then be distributed. It is to be noted that the constituentelements may be implemented as hardware (exclusive circuitry) as amatter of course.

In other words, in each of the above embodiments, each of theconstituent elements may be configured as exclusive hardware, or may berealized by executing a software program suitable for the constituentelement. Each of the constituent elements may be realized by means ofthe program executing unit such as a CPU or a processor reading thesoftware program recorded on a recording medium such as a hard disk or asemiconductor memory and executing the software program.

In other words, each of the image encoding device and the image decodingdevice includes processing circuitry and storage electrically connectedto the processing circuitry (this storage is accessible from theprocessing circuitry). The processing circuitry includes at least one ofthe exclusive hardware and the program executing unit, and executesprocessing using the storage. In addition, when the processing circuitryincludes the program executing unit, the storage stores the softwareprogram which is executed by the program executing unit.

Here, the software which implements the image encoding device in each ofthe embodiments is, for example, a program below.

The program causes a computer to execute image encoding method forencoding, on a per field basis, a plurality of pictures classified intoa plurality of layers for which reference from a picture belonging to ahigher layer to a picture belonging to a lower layer is prohibited, theplurality of pictures including at least one picture that is encoded asa temporal sub-layer access (TSA) picture for which predeterminedreference is prohibited, the image encoding method including:determining whether a current picture included in the plurality ofpictures is the TSA picture or a trailing picture for which thepredetermined reference is permitted; and encoding the plurality ofpictures according to whether the current picture is the TSA picture orthe trailing picture, wherein the determining includes: determining thecurrent picture to be the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is encoded earlier than a second field in a pair offields in a frame; and determining the current picture to be thetrailing picture when the current picture belongs to the highest layeror corresponds to the second field that is encoded later than the firstfield in the pair of fields.

The program may cause a computer to execute an image decoding method fordecoding, on a per field basis, a plurality of pictures classified intoa plurality of layers for which reference from a picture belonging to ahigher layer to a picture belonging to a lower layer is prohibited, theplurality of pictures including at least one picture that is decoded asa temporal sub-layer access (TSA) picture for which predeterminedreference is prohibited, the image decoding method including:identifying whether a current picture included in the plurality ofpictures is the TSA picture or a trailing picture for which thepredetermined reference is permitted; and decoding the plurality ofpictures according to whether the current picture is the TSA picture orthe trailing picture, wherein the identifying includes: identifying thecurrent picture as the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is decoded earlier than a second field in a pair offields in a frame; and identifying the current picture as the trailingpicture when the current picture belongs to the highest layer orcorresponds to the second field that is decoded later than the firstfield in the pair of fields.

The constituent elements may be circuits. All of these circuits may beintegrated into a single circuit, or may be configured as separatecircuits. Alternatively, each of the constituent elements may beimplemented as a general processor or as an exclusive processor.

Alternatively, a process executed by a particular one of the processingunits may be executed by another one of the processing units.Alternatively, the execution order of the processes may be changed, orsome of the processes may be executed in parallel. Alternatively, animage encoding and decoding device may include the image encoding deviceand the image decoding device.

In addition, the processes described in each of the embodiments may beexecuted in centralized processing using a single device (system), ormay be realized in distributed processing using a plurality of devices.The program may be executed by one or more computers. In other words,one computer may execute the program in centralized processing, or somecomputers may execute the program in distributed processing.

The herein disclosed subject matter is to be considered descriptive andillustrative only, and the appended Claims are of a scope intended tocover and encompass not only the particular embodiments disclosed, butalso equivalent structures, methods, and/or uses.

Embodiment 5

The processing described in each of embodiments can be simplyimplemented in an independent computer system, by recording, in arecording medium, one or more programs for implementing theconfigurations of the moving picture encoding method (image encodingmethod) and the moving picture decoding method (image decoding method)described in each of embodiments. The recording media may be anyrecording media as long as the program can be recorded, such as amagnetic disk, an optical disk, a magnetic optical disk, an IC card, anda semiconductor memory.

Hereinafter, the applications to the moving picture encoding method(image encoding method) and the moving picture decoding method (imagedecoding method) described in each of embodiments and systems usingthereof will be described. The system has a feature of having an imagecoding apparatus that includes an image encoding apparatus using theimage encoding method and an image decoding apparatus using the imagedecoding method. Other configurations in the system can be changed asappropriate depending on the cases.

FIG. 17 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106, ex107, ex108, ex109, and ex110 which arefixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 17, and a combination inwhich any of the elements are connected is acceptable. In addition, eachdevice may be directly connected to the telephone network ex104, ratherthan via the base stations ex106 to ex110 which are the fixed wirelessstations. Furthermore, the devices may be interconnected to each othervia a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital camera, is capable ofcapturing both still images and video. Furthermore, the cellular phoneex114 may be the one that meets any of the standards such as GlobalSystem for Mobile Communications (GSM) (registered trademark), CodeDivision Multiple Access (CDMA), Wideband-Code Division Multiple Access(W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of images of alive show and others. In such a distribution, a content (for example,video of a music live show) captured by the user using the camera ex113is encoded as described above in each of embodiments (i.e., the camerafunctions as the image encoding apparatus according to an aspect of thepresent disclosure), and the encoded content is transmitted to thestreaming server ex103. On the other hand, the streaming server ex103carries out stream distribution of the transmitted content data to theclients upon their requests. The clients include the computer ex111, thePDA ex112, the camera ex113, the cellular phone ex114, and the gamemachine ex115 that are capable of decoding the above-mentioned encodeddata. Each of the devices that have received the distributed datadecodes and reproduces the encoded data (i.e., functions as the imagedecoding apparatus according to an aspect of the present disclosure).

The captured data may be encoded by the camera ex113 or the streamingserver ex103 that transmits the data, or the encoding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The encoding processes may be performed bythe camera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding processes may be performed by an LSI ex500generally included in each of the computer ex111 and the devices. TheLSI ex500 may be configured of a single chip or a plurality of chips.Software for coding video may be integrated into some type of arecording medium (such as a CD-ROM, a flexible disk, and a hard disk)that is readable by the computer ex111 and others, and the codingprocesses may be performed using the software. Furthermore, when thecellular phone ex114 is equipped with a camera, the video data obtainedby the camera may be transmitted. The video data is data encoded by theLSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients may receive and reproduce the encodeddata in the content providing system ex100. In other words, the clientscan receive and decode information transmitted by the user, andreproduce the decoded data in real time in the content providing systemex100, so that the user who does not have any particular right andequipment can implement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the moving picture coding apparatus (image coding apparatus)described in each of embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 18. More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data encoded bythe moving picture encoding method described in each of embodiments(i.e., data encoded by the image encoding apparatus according to anaspect of the present disclosure). Upon receipt of the multiplexed data,the broadcast satellite ex202 transmits radio waves for broadcasting.Then, a home-use antenna ex204 with a satellite broadcast receptionfunction receives the radio waves. Next, a device such as a television(receiver) ex300 and a set top box (STB) ex217 decodes the receivedmultiplexed data, and reproduces the decoded data (i.e., functions asthe image decoding apparatus according to an aspect of the presentdisclosure).

Furthermore, a reader/recorder ex218 (i) reads and decodes themultiplexed data recorded on a recording medium ex215, such as a DVD anda BD, or (i) encodes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on theencoded data. The reader/recorder ex218 can include the moving picturedecoding apparatus or the moving picture encoding apparatus as shown ineach of embodiments. In this case, the reproduced video signals aredisplayed on the monitor ex219, and can be reproduced by another deviceor system using the recording medium ex215 on which the multiplexed datais recorded. It is also possible to implement the moving picturedecoding apparatus in the set top box ex217 connected to the cable ex203for a cable television or to the antenna ex204 for satellite and/orterrestrial broadcasting, so as to display the video signals on themonitor ex219 of the television ex300. The moving picture decodingapparatus may be implemented not in the set top box but in thetelevision ex300.

FIG. 19 illustrates the television (receiver) ex300 that uses the movingpicture encoding method and the moving picture decoding method describedin each of embodiments. The television ex300 includes: a tuner ex301that obtains or provides multiplexed data obtained by multiplexing audiodata onto video data, through the antenna ex204 or the cable ex203, etc.that receives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data encoded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 that code each of audio data and video data,(which function as the image coding apparatus according to the aspectsof the present disclosure); and an output unit ex309 including a speakerex307 that provides the decoded audio signal, and a display unit ex308that displays the decoded video signal, such as a display. Furthermore,the television ex300 includes an interface unit ex317 including anoperation input unit ex312 that receives an input of a user operation.Furthermore, the television ex300 includes a control unit ex310 thatcontrols overall each constituent element of the television ex300, and apower supply circuit unit ex311 that supplies power to each of theelements. Other than the operation input unit ex312, the interface unitex317 may include: a bridge ex313 that is connected to an externaldevice, such as the reader/recorder ex218; a slot unit ex314 forenabling attachment of the recording medium ex216, such as an SD card; adriver ex315 to be connected to an external recording medium, such as ahard disk; and a modem ex316 to be connected to a telephone network.Here, the recording medium ex216 can electrically record informationusing a non-volatile/volatile semiconductor memory element for storage.The constituent elements of the television ex300 are connected to eachother through a synchronous bus.

First, the configuration in which the television ex300 decodesmultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon a user operation through a remote controllerex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside, respectively. When the output unit ex309 provides thevideo signal and the audio signal, the signals may be temporarily storedin buffers ex318 and ex319, and others so that the signals arereproduced in synchronization with each other. Furthermore, thetelevision ex300 may read multiplexed data not through a broadcast andothers but from the recording media ex215 and ex216, such as a magneticdisk, an optical disk, and a SD card. Next, a configuration in which thetelevision ex300 encodes an audio signal and a video signal, andtransmits the data outside or writes the data on a recording medium willbe described. In the television ex300, upon a user operation through theremote controller ex220 and others, the audio signal processing unitex304 encodes an audio signal, and the video signal processing unitex305 encodes a video signal, under control of the control unit ex310using the encoding method described in each of embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the encoded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in thebuffers ex320 and ex321, and others so that the signals are reproducedin synchronization with each other. Here, the buffers ex318, ex319,ex320, and ex321 may be plural as illustrated, or at least one buffermay be shared in the television ex300. Furthermore, data may be storedin a buffer so that the system overflow and underflow may be avoidedbetween the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may encode the obtained data. Although thetelevision ex300 can encode, multiplex, and provide outside data in thedescription, it may be capable of only receiving, decoding, andproviding outside data but not the encoding, multiplexing, and providingoutside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may code the multiplexed data, and the televisionex300 and the reader/recorder ex218 may share the coding partly.

As an example, FIG. 20 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or onan optical disk. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot in a recording surface of the recording medium ex215 thatis an optical disk to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. The disk motor ex405 rotates therecording medium ex215. The servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 21 illustrates the recording medium ex215 that is the optical disk.On the recording surface of the recording medium ex215, guide groovesare spirally formed, and an information track ex230 records, in advance,address information indicating an absolute position on the diskaccording to change in a shape of the guide grooves. The addressinformation includes information for determining positions of recordingblocks ex231 that are a unit for recording data. Reproducing theinformation track ex230 and reading the address information in anapparatus that records and reproduces data can lead to determination ofthe positions of the recording blocks. Furthermore, the recording mediumex215 includes a data recording area ex233, an inner circumference areaex232, and an outer circumference area ex234. The data recording areaex233 is an area for use in recording the user data. The innercircumference area ex232 and the outer circumference area ex234 that areinside and outside of the data recording area ex233, respectively arefor specific use except for recording the user data. The informationreproducing/recording unit 400 reads and writes encoded audio, encodedvideo data, or multiplexed data obtained by multiplexing the encodedaudio and video data, from and on the data recording area ex233 of therecording medium ex215.

Although an optical disk having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disk is notlimited to such, and may be an optical disk having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disk may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disk and for recording information havingdifferent layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be a configuration, for example, includinga GPS receiving unit from the configuration illustrated in FIG. 19. Thesame will be true for the configuration of the computer ex111, thecellular phone ex114, and others.

FIG. 22A illustrates the cellular phone ex114 that uses the movingpicture coding method described in embodiments. The cellular phone ex114includes: an antenna ex350 for transmitting and receiving radio wavesthrough the base station ex110; a camera unit ex365 capable of capturingmoving and still images; and a display unit ex358 such as a liquidcrystal display for displaying the data such as decoded video capturedby the camera unit ex365 or received by the antenna ex350. The cellularphone ex114 further includes: a main body unit including an operationkey unit ex366; an audio output unit ex357 such as a speaker for outputof audio; an audio input unit ex356 such as a microphone for input ofaudio; a memory unit ex367 for storing captured video or still pictures,recorded audio, coded data of the received video, the still pictures,e-mails, or others; and a slot unit ex364 that is an interface unit fora recording medium that stores data in the same manner as the memoryunit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 22B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keyunit ex366 is connected mutually, via a synchronous bus ex370, to apower supply circuit unit ex361, an operation input control unit ex362,a video signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex357.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation key unitex366 and others of the main body is sent out to the main control unitex360 via the operation input control unit ex362. The main control unitex360 causes the modulation/demodulation unit ex352 to perform spreadspectrum processing on the text data, and the transmitting and receivingunit ex351 performs the digital-to-analog conversion and the frequencyconversion on the resulting data to transmit the data to the basestation ex110 via the antenna ex350. When an e-mail is received,processing that is approximately inverse to the processing fortransmitting an e-mail is performed on the received data, and theresulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand encodes video signals supplied from the camera unit ex365 using themoving picture encoding method shown in each of embodiments (i.e.,functions as the image encoding apparatus according to the aspect of thepresent disclosure), and transmits the encoded video data to themultiplexing/demultiplexing unit ex353. In contrast, during when thecamera unit ex365 captures video, still images, and others, the audiosignal processing unit ex354 encodes audio signals collected by theaudio input unit ex356, and transmits the encoded audio data to themultiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the encoded videodata supplied from the video signal processing unit ex355 and theencoded audio data supplied from the audio signal processing unit ex354,using a predetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the multiplexed data, and the transmitting and receivingunit ex351 performs digital-to-analog conversion and frequencyconversion on the data so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bit stream, and supplies the video signal processing unitex355 with the encoded video data and the audio signal processing unitex354 with the encoded audio data, through the synchronous bus ex370.The video signal processing unit ex355 decodes the video signal using amoving picture decoding method corresponding to the moving pictureencoding method shown in each of embodiments (i.e., functions as theimage decoding apparatus according to the aspect of the presentdisclosure), and then the display unit ex358 displays, for instance, thevideo and still images included in the video file linked to the Web pagevia the LCD control unit ex359. Furthermore, the audio signal processingunit ex354 decodes the audio signal, and the audio output unit ex357provides the audio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 probably have 3 types of implementationconfigurations including not only (i) a transmitting and receivingterminal including both an encoding apparatus and a decoding apparatus,but also (ii) a transmitting terminal including only an encodingapparatus and (iii) a receiving terminal including only a decodingapparatus. Although the digital broadcasting system ex200 receives andtransmits the multiplexed data obtained by multiplexing audio data ontovideo data in the description, the multiplexed data may be data obtainedby multiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving picture coding method in each of embodiments can beused in any of the devices and systems described. Thus, the advantagesdescribed in each of embodiments can be obtained.

Furthermore, various modifications and revisions can be made in any ofthe embodiments in the present disclosure.

Embodiment 6

Video data can be generated by switching, as necessary, between (i) themoving picture encoding method or the moving picture encoding apparatusshown in each of embodiments and (ii) a moving picture encoding methodor a moving picture encoding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconform cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture encoding method and by themoving picture encoding apparatus shown in each of embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG-2 Transport Stream format.

FIG. 23 illustrates a structure of the multiplexed data. As illustratedin FIG. 23, the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of the movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the primary video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is encoded in the moving picture encoding method or by themoving picture encoding apparatus shown in each of embodiments, or in amoving picture encoding method or by a moving picture encoding apparatusin conformity with a conventional standard, such as MPEG-2, MPEG-4 AVC,and VC-1. The audio stream is encoded in accordance with a standard,such as Dolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linearPCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary audio to be mixed with the primary audio.

FIG. 24 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 25 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 25 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 25, the video stream is divided into pictures as I pictures, Bpictures, and P pictures each of which is a video presentation unit, andthe pictures are stored in a payload of each of the PES packets. Each ofthe PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 26 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The source packets are arranged in the multiplexed dataas shown at the bottom of FIG. 26. The numbers incrementing from thehead of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 27 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 28. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 28, the multiplexed data information includes asystem rate, a reproduction start time, and a reproduction end time. Thesystem rate indicates the maximum transfer rate at which a system targetdecoder to be described later transfers the multiplexed data to a PIDfilter. The intervals of the ATSs included in the multiplexed data areset to not higher than a system rate. The reproduction start timeindicates a PTS in a video frame at the head of the multiplexed data. Aninterval of one frame is added to a PTS in a video frame at the end ofthe multiplexed data, and the PTS is set to the reproduction end time.

As shown in FIG. 29, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In the present embodiment, the multiplexed data to be used is of astream type included in the PMT. Furthermore, when the multiplexed datais recorded on a recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, the moving picture encoding method or the moving pictureencoding apparatus described in each of embodiments includes a step or aunit for allocating unique information indicating video data generatedby the moving picture encoding method or the moving picture encodingapparatus in each of embodiments, to the stream type included in the PMTor the video stream attribute information. With the configuration, thevideo data generated by the moving picture encoding method or the movingpicture encoding apparatus described in each of embodiments can bedistinguished from video data that conforms to another standard.

Furthermore, FIG. 30 illustrates steps of the moving picture decodingmethod according to the present embodiment. In Step exS100, the streamtype included in the PMT or the video stream attribute informationincluded in the multiplexed data information is obtained from themultiplexed data. Next, in Step exS101, it is determined whether or notthe stream type or the video stream attribute information indicates thatthe multiplexed data is generated by the moving picture encoding methodor the moving picture encoding apparatus in each of embodiments. When itis determined that the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving picture encoding method or the moving picture encoding apparatusin each of embodiments, in Step exS102, decoding is performed by themoving picture decoding method in each of embodiments. Furthermore, whenthe stream type or the video stream attribute information indicatesconformance to the conventional standards, such as MPEG-2, MPEG-4 AVC,and VC-1, in Step exS103, decoding is performed by a moving picturedecoding method in conformity with the conventional standards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving picture decoding method or the moving picture decoding apparatusthat is described in each of embodiments can perform decoding. Even whenmultiplexed data that conforms to a different standard is input, anappropriate decoding method or apparatus can be selected. Thus, itbecomes possible to decode information without any error. Furthermore,the moving picture encoding method or apparatus, or the moving picturedecoding method or apparatus in the present embodiment can be used inthe devices and systems described above.

Embodiment 7

Each of the moving picture coding method and the moving picture codingapparatus in each of embodiments is typically achieved in the form of anintegrated circuit or a Large Scale Integrated (LSI) circuit. As anexample of the LSI, FIG. 31 illustrates a configuration of the LSI ex500that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when encoding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AVIO ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507encodes an audio signal and/or a video signal. Here, the encoding of thevideo signal is the encoding described in each of embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes theencoded audio data and the encoded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recordingmedium ex215. When data sets are multiplexed, the data should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose. Such a programmable logic devicecan typically execute the moving picture coding method according to anyof the above embodiments, by loading or reading from a memory or thelike one or more programs that are included in software or firmware.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present disclosureis applied to biotechnology.

Embodiment 8

When video data generated in the moving picture encoding method or bythe moving picture encoding apparatus described in each of embodimentsis decoded, compared to when video data that conforms to a conventionalstandard, such as MPEG-2, MPEG-4 AVC, and VC-1 is decoded, theprocessing amount probably increases. Thus, the LSI ex500 needs to beset to a driving frequency higher than that of the CPU ex502 to be usedwhen video data in conformity with the conventional standard is decoded.However, there is a problem that the power consumption increases whenthe driving frequency is set higher.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 32illustrates a configuration ex800 in the present embodiment. A drivingfrequency switching unit ex803 sets a driving frequency to a higherdriving frequency when video data is generated by the moving pictureencoding method or the moving picture encoding apparatus described ineach of embodiments. Then, the driving frequency switching unit ex803instructs a decoding processing unit ex801 that executes the movingpicture decoding method described in each of embodiments to decode thevideo data. When the video data conforms to the conventional standard,the driving frequency switching unit ex803 sets a driving frequency to alower driving frequency than that of the video data generated by themoving picture encoding method or the moving picture encoding apparatusdescribed in each of embodiments. Then, the driving frequency switchingunit ex803 instructs the decoding processing unit ex802 that conforms tothe conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 31.Here, each of the decoding processing unit ex801 that executes themoving picture decoding method described in each of embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 31. TheCPU ex502 determines to which standard the video data conforms. Then,the driving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on the signal from the CPUex502. For example, the identification information described inEmbodiment 6 is probably used for identifying the video data. Theidentification information is not limited to the one described inEmbodiment 6 but may be any information as long as the informationindicates to which standard the video data conforms. For example, whenwhich standard video data conforms to can be determined based on anexternal signal for determining that the video data is used for atelevision or a disk, etc., the determination may be made based on suchan external signal. Furthermore, the CPU ex502 selects a drivingfrequency based on, for example, a look-up table in which the standardsof the video data are associated with the driving frequencies as shownin FIG. 34. The driving frequency can be selected by storing the look-uptable in the buffer ex508 and in an internal memory of an LSI, and withreference to the look-up table by the CPU ex502.

FIG. 33 illustrates steps for executing a method in the presentembodiment. First, in Step exS200, the signal processing unit ex507obtains identification information from the multiplexed data. Next, inStep exS201, the CPU ex502 determines whether or not the video data isgenerated by the encoding method and the encoding apparatus described ineach of embodiments, based on the identification information. When thevideo data is generated by the moving picture encoding method and themoving picture encoding apparatus described in each of embodiments, inStep exS202, the CPU ex502 transmits a signal for setting the drivingfrequency to a higher driving frequency to the driving frequency controlunit ex512. Then, the driving frequency control unit ex512 sets thedriving frequency to the higher driving frequency. On the other hand,when the identification information indicates that the video dataconforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1, in Step exS203, the CPU ex502 transmits a signal for setting thedriving frequency to a lower driving frequency to the driving frequencycontrol unit ex512. Then, the driving frequency control unit ex512 setsthe driving frequency to the lower driving frequency than that in thecase where the video data is generated by the moving picture encodingmethod and the moving picture encoding apparatus described in each ofembodiment.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the processing amount for decoding is larger, thedriving frequency may be set higher, and when the processing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when theprocessing amount for decoding video data in conformity with MPEG-4 AVCis larger than the processing amount for decoding video data generatedby the moving picture encoding method and the moving picture encodingapparatus described in each of embodiments, the driving frequency isprobably set in reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture encoding method and the moving pictureencoding apparatus described in each of embodiments, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set higher. When the identification information indicates thatthe video data conforms to the conventional standard, such as MPEG-2,MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or theapparatus including the LSI ex500 is probably set lower. As anotherexample, when the identification information indicates that the videodata is generated by the moving picture encoding method and the movingpicture encoding apparatus described in each of embodiments, the drivingof the CPU ex502 does not probably have to be suspended. When theidentification information indicates that the video data conforms to theconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the drivingof the CPU ex502 is probably suspended at a given time because the CPUex502 has extra processing capacity. Even when the identificationinformation indicates that the video data is generated by the movingpicture encoding method and the moving picture encoding apparatusdescribed in each of embodiments, in the case where the CPU ex502 hasextra processing capacity, the driving of the CPU ex502 is probablysuspended at a given time. In such a case, the suspending time isprobably set shorter than that in the case where when the identificationinformation indicates that the video data conforms to the conventionalstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Embodiment 9

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a cellular phone. In order to enable decoding theplurality of video data that conforms to the different standards, thesignal processing unit ex507 of the LSI ex500 needs to conform to thedifferent standards. However, the problems of increase in the scale ofthe circuit of the LSI ex500 and increase in the cost arise with theindividual use of the signal processing units ex507 that conform to therespective standards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 35A showsan example of the configuration. For example, the moving picturedecoding method described in each of embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy encoding, inverse quantization,deblocking filtering, and motion compensated prediction. The details ofprocessing to be shared probably include use of a decoding processingunit ex902 that conforms to MPEG-4 AVC. In contrast, a dedicateddecoding processing unit ex901 is probably used for other processingwhich is unique to an aspect of the present disclosure and does notconform to MPEG-4 AVC. Since the aspect of the present disclosure ischaracterized by motion compensation in particular, for example, thededicated decoding processing unit ex901 is used for motioncompensation. Otherwise, the decoding processing unit is probably sharedfor one of the entropy decoding, deblocking filtering, and inversequantization, or all of the processing. The decoding processing unit forimplementing the moving picture decoding method described in each ofembodiments may be shared for the processing to be shared, and adedicated decoding processing unit may be used for processing unique tothat of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 35B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to an aspect of the present disclosure, a dedicated decodingprocessing unit ex1002 that supports the processing unique to anotherconventional standard, and a decoding processing unit ex1003 thatsupports processing to be shared between the moving picture decodingmethod according to the aspect of the present disclosure and theconventional moving picture decoding method. Here, the dedicateddecoding processing units ex1001 and ex1002 are not necessarilyspecialized for the processing according to the aspect of the presentdisclosure and the processing of the conventional standard,respectively, and may be the ones capable of implementing generalprocessing. Furthermore, the configuration of the present embodiment canbe implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving picture decoding methodaccording to the aspect of the present disclosure and the moving picturedecoding method in conformity with the conventional standard.

INDUSTRIAL APPLICABILITY

The image encoding device, the image decoding device, and the imageencoding and decoding device, and the methods thereof according to oneor more exemplary embodiments disclosed herein are applicable to, forexample, television receivers, digital video recorders, car navigationsystems, mobile telephones, digital cameras, digital video cameras, etc.

1. An image encoding method for encoding, on a per field basis, aplurality of pictures classified into a plurality of layers for whichreference from a picture belonging to a higher layer to a picturebelonging to a lower layer is prohibited, the plurality of picturesincluding at least one picture that is encoded as a temporal sub-layeraccess (TSA) picture for which predetermined reference is prohibited,the image encoding method comprising: determining whether a currentpicture included in the plurality of pictures is the TSA picture or atrailing picture for which the predetermined reference is permitted; andencoding the plurality of pictures according to whether the currentpicture is the TSA picture or the trailing picture, wherein thedetermining includes: determining the current picture to be the TSApicture when the current picture does not belong to a highest layer inthe plurality of layers and corresponds to a first field that is encodedearlier than a 20 second field in a pair of fields in a frame; anddetermining the current picture to be the trailing picture when thecurrent picture belongs to the highest layer or corresponds to thesecond field that is encoded later than the first field in the pair offields.
 2. The image encoding method according to claim 1, wherein theencoding includes: encoding an unencoded picture with the predeterminedreference from the unencoded picture to an encoded picture beingprohibited, when the current picture is determined to be the TSApicture, the unencoded picture being the current picture or a picturefollowing the current picture in coding order in the plurality ofpictures, the encoded picture being a picture preceding the currentpicture in coding order in the plurality of pictures and belonging to alayer to which the current picture belongs or a layer lower than thelayer to which the current picture belongs; and encoding the unencodedpicture with the predetermined reference being permitted, when thecurrent picture is determined to be the trailing picture.
 3. The imageencoding method according to claim 1, wherein the determining includes:determining the current picture to be the TSA picture when the currentpicture does not belong to the highest layer and corresponds to thefirst field which is a top field; and determining the current picture tobe the trailing picture when the current picture belongs to the highestlayer or corresponds to the 15 second field which is a bottom field. 4.The image encoding method according to claim 1, wherein the determiningincludes: determining the current picture to be the TSA picture when thecurrent picture does not belong to the highest layer and corresponds tothe first field that immediately precedes the second field in codingorder; and determining the current picture to be the trailing picturewhen the current picture belongs to the highest layer or corresponds tothe second field that immediately follows the first field in codingorder.
 5. The image encoding method according to claim 1, the imageencoding method further includes encoding a picture type indicatingwhether the current picture is the TSA picture or the trailing picture.6. An image decoding method for decoding, on a per field basis, aplurality of pictures classified into a plurality of layers for whichreference from a picture belonging to a higher layer to a picturebelonging to a lower layer is prohibited, the plurality of picturesincluding at least one picture that is decoded as a temporal sub-layeraccess (TSA) picture for which predetermined reference is prohibited,the image decoding method comprising: identifying whether a currentpicture included in the plurality of pictures is the TSA picture or atrailing picture for which the predetermined reference is permitted; anddecoding the plurality of pictures according to whether the currentpicture is the TSA picture or the trailing picture, wherein theidentifying includes: identifying the current picture as the TSA picturewhen the current picture does not belong to a highest layer in theplurality of layers and corresponds to a first field that is decodedearlier than a second field in a pair of fields in a frame; andidentifying the current picture as the trailing picture when the currentpicture belongs to the highest layer or corresponds to the second fieldthat is decoded later than the first field in the pair of fields.
 7. Theimage decoding method according to claim 6, wherein the decodingincludes: decoding an undecoded picture with the predetermined referencefrom the undecoded picture to a decoded picture being prohibited, whenthe current picture is identified as the TSA picture, the undecodedpicture being the current picture or a picture following the currentpicture in decoding order in the plurality of pictures, the decodedpicture being a picture preceding the current picture in decoding orderin the plurality of pictures and belonging to a layer to which thecurrent picture belongs or a layer lower than the layer to which thecurrent picture belongs; and decoding the undecoded picture with thepredetermined reference being permitted, when the current picture isidentified as the trailing picture.
 8. The image decoding methodaccording to claim 6, wherein the identifying includes: identifying thecurrent picture as the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field which isa top field; and identifying the current picture as the trailing picturewhen the current picture belongs to the highest layer or corresponds tothe second field which is a bottom field.
 9. The image decoding methodaccording to claim 6, wherein the identifying includes: identifying thecurrent picture as the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field thatimmediately precedes the second field in decoding order; and identifyingthe current picture as the trailing picture when the current picturebelongs to the highest layer or corresponds to the second field thatimmediately follows the first field in decoding order.
 10. The imagedecoding method according to claim 6, the image decoding method furtherincludes decoding a picture type indicating whether the current pictureis the TSA picture or the trailing picture, wherein the identifyingincludes: identifying the current picture as the TSA picture accordingto the picture type decoded in the decoding, when the current picturedoes not belong to the highest layer and corresponds to the first field;and identifying the current picture as the trailing picture according tothe picture type decoded in the decoding, when the current picturebelongs to the highest layer or corresponds to the second field.
 11. Theimage decoding method according to claim 10, further comprising checkingwhether the picture type decoded in the decoding is correct, wherein thechecking includes: checking that the picture type decoded in thedecoding is correct by checking that the picture type indicates thecurrent picture as the TSA picture when the current picture does notbelong to the highest layer and corresponds to the first field; andchecking that the picture type decoded in the decoding is correct bychecking that the picture type indicates the current picture as thetrailing picture when the current picture belongs to the highest layeror corresponds to the second field.
 12. The image decoding methodaccording to claim 11, wherein the checking further includes controllingthe decoding of the plurality of pictures so as to prevent decoding ofthe current picture when the picture type decoded in the decoding of thepicture type is incorrect.
 13. An image encoding device which encodes,on a per field basis, a plurality of pictures classified into aplurality of layers for which reference from a picture belonging to ahigher layer to a picture belonging to a lower layer is prohibited, theplurality of pictures including at least one picture that is encoded asa temporal sub-layer access (TSA) picture for which predeterminedreference is prohibited, the image encoding device comprising: adetermining unit configured to determine whether a current pictureincluded in the plurality of pictures is the TSA picture or a trailingpicture for which the predetermined reference is permitted; and anencoding unit configured to encode the plurality of pictures accordingto whether the current picture is the TSA picture or the trailingpicture, wherein the determining unit is configured to: determine thecurrent picture to be the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is encoded earlier than a second field in a pair offields in a frame; and determine the current picture to be the trailingpicture when the current picture belongs to the highest layer orcorresponds to the second field that is encoded later than the firstfield in the pair of fields.
 14. An image decoding device which decodes,on a per field basis, a plurality of pictures classified into aplurality of layers for which reference from a picture belonging to ahigher layer to a picture belonging to a lower layer is prohibited, theplurality of pictures including at least one picture that is decoded asa temporal sub-layer access (TSA) picture for which predeterminedreference is prohibited, the image decoding device comprising: anidentifying unit configured to identify whether a current pictureincluded in the plurality of pictures is the TSA picture or a trailingpicture for which the predetermined reference is permitted; and adecoding unit configured to decode the plurality of pictures accordingto whether the current picture is the TSA picture or the trailingpicture, wherein the identifying unit is configured to: identify thecurrent picture as the TSA picture when the current picture does notbelong to a highest layer in the plurality of layers and corresponds toa first field that is decoded earlier than a second field in a pair offields in a frame; and identify the current picture as the trailingpicture when the current picture belongs to the highest layer orcorresponds to the second field that is decoded later than the firstfield in the pair of fields.
 15. An image encoding and decoding devicecomprising: the image encoding device according to claim 13; and animage decoding device which decodes, on a per field basis, a pluralityof pictures classified into a plurality of layers for which referencefrom a picture belonging to a higher layer to a picture belonging to alower layer is prohibited, the plurality of pictures including at leastone picture that is decoded as a temporal sub-layer access (TSA) picturefor which predetermined reference is prohibited, the image decodingdevice including: an identifying unit configured to identify whether acurrent picture included in the plurality of pictures is the TSA pictureor a trailing picture for which the predetermined reference ispermitted; and a decoding unit configured to decode the plurality ofpictures according to whether the current picture is the TSA picture orthe trailing picture, wherein the identifying unit is configured to:identify the current picture as the TSA picture when the current picturedoes not belong to a highest layer in the plurality of layers andcorresponds to a first field that is decoded earlier than a second fieldin a pair of fields in a frame; and identify the current picture as thetrailing picture when the current picture belongs to the highest layeror corresponds to the second field that is decoded later than the firstfield in the pair of fields.